Portable grinding device



June 17, 1941. c. ERDMAN PORTABLE GRINDING DEVICE Filed Aug. '1, 1939 2 Sheets-Sheet 1 INVEN TOR. 6141 w/v [ROMA/V A TTORNEY.

Jun 17, 1941. c, ERDMAN PORTABLE GRINDING nmvrcs Filed Aug. 1, 1939 2 Sheets-Sheet 2 MA n NM M 5 A W. M C 7 O Y Y B 3 E a Z 1 aaaw w IatenterI June 17, 19 41 UNITED STATES PATENT OFFICE ron'iilgm GRINDING DEVICE calvl fizramm, Claremont, Calif.

Applicatioifiugust 1',-1939, Serial No. 287,709

2 Claims.

The present invention pertains to a portable grinding and sharpening device which is particularly adapted for use on lawnmowers although it may be used in sharpening various other tools and may be used as a portable grinder for numerous household and farm equipment. Generally stated, the invention pertains to a device whereby lawnmowers employing spiral bladesmay be sharpened without the necessity of dismantling the lawnmower.

The device of the present invention is light, portable and may be removably attached to a lawnmower so that the blades thereof can be sharpened readily and quickly without dismantling the lawnmower. Generally stated, the device includes a frame provided with a guide rod, the grinding unit being pivotally mounted upon such guide rod. The frame is removably attached to a lawnmower in such manner that the guide rod parallels the shaft upon which the blades are mounted. Means are provided on the device whereby the unit may be manually moved along the guide rod from one end to the other of the blade. Since the blades are arranged in spiral form around their rotational axis, stop means are provided on the device whereby these blades are made to present their edges to the grinding wheel carried by the unit as such unit is moved from one end to the other of the blade assembly.

An object of the present invention, therefore, is to disclose and provide a portable grinding andsharpening device which may be used in sharpening lawnmowers without taking the same apart.

A further object is to provide a portable grinding and sharpening unit which may be readily releasably attached to a lawnmower and used 'in sharpening the knives or cutting blades of the device.

A stfll further object is to provide a device which may be used in sharpening various household and farm equipment.

Other objects, advantages, characteristics, uses and adaptations of the device will become apparent to those skilled in the art from the description given hereinafter. In order to facilitate understanding, reference will be had to the appended drawings, in which:

Fig. 1 is a side view of the devil, partly in section, and in operative position on a lawnmower.

Fig. 2 is an enlarged view of the grinding wheel end of the device in position for sharpening the cutter bar of a lawnmower.

Fig. 3 is a transverse section taken along the plane IIIIII of Fig. 1.

Fig. 4 is a view taken along the plane IV-IV of Fig. 1., 1

Fig. 5 is a view of the bottom of the grinding unit carriage.

Figs. 6 and '1 are side and front views respectively of a modified form of means for adjustably and releasably holding the device in position during sharpening of a lawnmower.

A lawnmower ordinarily includes'a main shaft l carrying spiders 2 which support the knives 3, 4, etc., these knives being arranged around the shaft I in the form of spirals. The shaft I is driven by suitable gearing within a gear case 5 and the entire device is supported in rolling contact with the ground on the wheels 8. A roller, indicated at I, also contacts with the ground.

In Fig. 1 the lawnmower is shown in an inverted position, resting against a wall or other support, since this is the position in which it may be most readily sharpened. In addition to the elements specifically referred to, .a lawnmower also includes a back bar 8 carrying the cutter bar 8, the cutter bar 9 cooperating with the edges of theknives 3, 4, et'c., in cutting the grass.

As shown in Figs. 1, 4 and 5, the device of this invention includes a frame I8 provided with a guide rod ll. Means are also provided for releasably connecting this frame It! to some member paralleling the guide rod I I. On most lawnmowers a'bar I2 connects the outer portions or gear cases 5, this bar I2 paralleling the driven mower shaft I. The bar I2 is also shown in Fig. 4 and it will be seen that the frame I0 is releasably connectalble to the bar I2 by means of an auxiliary U-shaped frame, generally indicated at I3, having the upstanding end portions I4 and I5, such upstanding portions being provided with perforations or apertures I8, I1. etc. The main frame III carries a reciprocable pin II! which is yieldably urged outwardly by means of a spring l9, this pin and spring being'retained within a housing 20 attached to the frame It! and provided with a portion 2i enclosing the upstanding members I4 and I5 of the auxiliary frame I3. The pin I8 may be moved by means of a. lever 22 pivoted as at 23 in the housing 28. a slot in the lower end of the lever 22 cooperating with a transverse pin extending from the locking pin I8. Manipulation of the levers 22 will withdraw the locking pins I8 from apertures in the ends of the auxiliary frame I3 and permit such auxiliary frame to be moved downwardly from the position indicated in Fig. 4 and to be retained in some other position by engagement of the locking pins II with an upper aperture or port, thereby raising the guide rod II to some predetermined point above the bar l2.

The auxiliary frame I 3 is attached to the rod I! by means of the hook-like members 24 attached to the bottom of the auxiliary frame l3, these hook-like members 24 being provided with thumb screws 25, or other means, adapted to lock the auxiliary frame on the rod l2.

It is to be noted that the frame I3 is provided with a lower portion embraced by the auxiliary frame I3 and a wider upper portion, such wider upper portion carrying the guide rod II. This permits the frame I3 to be attached to bars i2 on lawnmowers of diil'erent widths whereas the guide rod ii is sufliciently long to extend over even the widest lawnmower.

Pivotally mounted upon the guide rod II and slidable thereon is a grinding unit carriage generally indicated at 33 and extending transversely of the guide rod as shown in Fig. 5. One end of such carriage 33 may carry a motor 3| whereas the other end of the carriage may have a grinding wheel 32 suitably joumaled thereon as upon the shaft 33 which preferably parallels the guide rod II.

An operative connection exists between the motor and the grinding wheel 32 and as shown in Fig. 5, the motor shaft and pulley 34 may be connected to the shaft 33 of the grinding wheel by means of a belt 35. Preferably the motor 3| is mounted above and beyond the guide rod l I when the entire device is in position on a lawnmower to sharpen the same, the center of gravity of the motor 3i now tending to counterbalance the other end of the grinding unit carriage 33. An adjustably positionable guiding wheel 31 is carried by the free end of the carriage 33. As shown in Fig. 1, the guiding wheel 31 may be provided with a groove adapted to receive the edge of the cutting bar 3. The guiding wheel 31 may be mounted for rotation on one end of a bolt 33, such bolt passing through a suitable internally threaded bore having its axis preferably at right angles to the axis of the guide rod il. Means for holding the bolt in a predetermined position may be provided such as, for example, the set screw 33.

Means are also provided for guidingly directing the various blades 3, 4, etc., of the mower into engagement with the grinding wheel 32. As shown in the drawings, such means are indicated at 43 and comprise a member provided with a bent or arcuate lower portion 4| capable of being positioned adjacent the cutting surface of the grinding wheel 32 at various points. The member 43 may pass through a bore in the head of a bolt 42 rotatable in the side wall of the carriage 33 and capable of being locked in any desired position by means of a locking lever 43 threadably mounted on the bolt 42.

In operation the device is releasably attached to the bar l2 (or some other bar paralleling the mower shaft I) while the lawnmower is in substantially inverted position. The guiding wheel 31 is caused to rest against the cutter bar 3 and the bolt 33 is manipulated until the surface of the grinding wheel 32 contacts with the cutting edge of one of the knives 3, 4, or the like, at a desired angle. The stop member 43 is then manipulated by means of the locking lever 43 until it rests against the mower blade and supports the same in the desired position while the blade or knife is against the grinding wheel 32. Since the knife blades 3, 4 and the like are in the form of a spiral, the grinding unit carriage is moved to one end of the knife blades, the motor 3| started by actuating a switch such as the switch 45, and the entire grinding unit carriage is then moved along the guide rod ii with the guiding wheel 31 in contact with the cutting bar 3, the mower blade or knife being thus sharpened from one end to the other. A similar sharpening operation is then carried out onthe other mower blades in succession.

It will be noted that the edge of the blades, 3, 4, etc., may be hollow ground and the sharpness of the resulting edge may be varied by changing the position of the stop member 43 and the elevation of the guiding wheel 31.

If it is then desired to sharpen the cutter bar 3, the grinding unit carriage 33 is slightly lifted and moved so as to place the guiding wheel 31 against the back of the cutter bar 3, the elevating means 38 being manipulated so as to bring the grinding wheel 32 into contact with the edge of the cutting bar 3. The carriage 33 will have to be maintained in this position by hand, the wheel 31 being pressed against the back of the cutting bar 3 manually in order to prevent the grinding wheel 32 from cutting into the cutter bar 3 with unnecessary force. The stop member 43 may be adjusted so as to help support the carriage on the edge of the cutting bar 3, as shown in Fig. 2, and also prevent the spiral blades from accidentally contacting the grinding wheel.

Since the frames of many mowers are slightly warped, it may be desirable to adjustably position one end of guide bar II in frame l3 as by providing a slot 45 in the end of the frame, the nut 41 being tightened after a necessary adjustment is made.

It will be obvious to those skilled in the art that the U-shaped portion of the frame l3 may be so constructed as to permit the housing of the motor 3| to be swung beneath the bar Ii, thereby exposing the bottom of the carriage 33 and rendering the grinding wheel 32 accessible from the top. In this position the entire unit may be used for grinding and sharpening various small utensils such as knives, scissors, and the like.

In Figs. 6 and 'I a modified form of means for releasably attaching the main frame II to a bar such as the bar I 2, is shown. In this modified form the auxiliary frame 53 is provided with a flange 5| adapted to encircle one edge of the frame l3 and with another flange 52 having bent portions 53 and 54 encircling the other edge of the frame. These bent portions 53 and 54 are perforated or bored so as to slidably receive a bar 55 provided with a hook 53 at its lower end and an arm 51 at its upper end. A spring 53 yieldably urges the bar 55 upwardly by pressure against a pin 53 passing through such bar. The

auxiliary frame 53 is thus releasably attachable to the bar |2.. 'In order to adjustably position the auxiliary frame 53 with respect to the main frame l3, one edge of themain frame l3 may be provided with serrations or depressions 33 adapted to receive a key 6| carried by a lever arm 52 pivoted as at 63, a spring 64 tending to move the lever 32 and its key 3| into one of the selected depressions or serrations 33. Such key may be manually released when desired.

Although a'specific form of device has been described in detail, it will be understood that the grinding wheel may gravitationally rest upon numerous changes and modifications can be made from this exemplary form, and all adaptations or being manually slidable on said guide rod and including a grinding wheel journaled near one end of said carriage, a bent stop member adjacent said grinding wheel, means for adjustably varying the position of the end of said stop member with respect to said grinding wheel in three planes; a guiding wheel rotatably mounted on an adjustable support carried by said carriage adjacent said grinding wheel, and a motor carried by the other end of said carriage and tending to counterbalance said grinding wheel when the device is in position on a lawnmower, whereby a knife of a mower during grinding.

2. A portable grinding and sharpening device adapted for use on lawnmowers, which comprises: a frame including a relatively narrow lower portion and a wide upper portion provided with a guide rod; manually releasable means for removably connecting said frame to a member paralleling said guide rod; a grinding unit cairiage extending transversely of said guide rod and pivoted thereon, said carriage being manually slidable on said guide rod and including a grinding wheel journaled near one end of said carriage, a bent stop member adjacent said grinding wheel, means for adjustably varying the position of the end of said stop member with respect to said grinding wheel in three planes; a guiding wheel rotatably mounted on an adjustable support carried by said carriage adjacent said grinding wheel and a motor carried by the other end of said carriage and tending to counterbalance said grinding wheel when the device is in position on a lawnmower, whereby the.

grinding wheel may gravitationally rest upon a knife of a mower during grinding.

CALVIN ERDMAN. 

